Field of the Invention
The present invention relates to the field of materials and particularly to the field of graphene sheet materials.
Related Art
Presented below is background information on certain aspects of the present invention as they may relate to technical features referred to in the detailed description, but not necessarily described in detail. The discussion below should not be construed as an admission as to the relevance of the information to the claimed invention or the prior art effect of the material described.
Graphene is an intriguing material with properties that are distinct from those of other graphitic systems.1-5 The first samples of pristine graphene were obtained by ‘peeling off’2, 6 and epitaxial growth5, 7. Recently, the chemical reduction of graphite oxide was used to produce covalently functionalized single-layer graphene oxide.8-15 However, chemical approaches for the large-scale production of highly conducting graphene sheets remain elusive.
Several methods have been explored thus far to obtain graphene in solution phase via chemical routes. Graphite oxide (GO) was prepared by harsh oxidation using the Hummer's method.16 The as-made GO was electrically insulating but chemical reduction9, 10, 15 partially recovered the conductivity, albeit at values orders of magnitude below that of pristine graphene. Irreversible defects and disorder exist in the GO sheets.9, 10 The reduced GO exhibit non-metallic behavior, with the conductance decreasing by about three orders of magnitude upon cooling to low temperature,13 whereas pristine graphene is nearly metallic.2, 17 Li et al. reported pristine graphene nanoribbons (GNR) obtained by sonicating thermally exfoliated graphite in a 1,2-dichloroethane (DCE) solution of poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV).18 Nevertheless, the yield was low and most of the ribbons contained two or more layers. Despite these and other efforts,8, 15, 19-22 solution phase derivation of single-layer graphene with high electrical conductivity from widely available parent graphite materials has not been achieved at a large scale. The production of stable suspensions of graphene in organic solvents is also an important goal in chemical processing and other areas.